Hi all - I had a question.

I just started a full node using bitcoin core and it is currently syncing/validating the past blockchain and catching up. I understand that the default setting in bitcoin core is that non-wallet transaction data is not stored on your harddrive in the blockchain data. My questions are then:

1. How does my node verify/validate the past blocks without knowing the transactions from that block? I'm assuming other nodes don't store the transaction data so how is it that my node obtains the transactions to do a full validation of the particular block?

2. If the transactions are not stored on my computer, how do I have a full copy of the blockchain? I thought this was one of the points of running a node - you have a full backup of the entire blockchain. How could I reproduce the entire blockchain (if needed) without having the transaction data within each block?

3. If transactions are not stored, what exactly is stored in the block data and how is that useful?

4. If transaction data is not stored in the block data of your computer (ie: txindex=0), how can you reproduce all the transactions if needed without having to download anything or connect to intenet to get it from other nodes if say you were the last node with a copy of the blockchain (eg: in case of an emergency if say, theoretically, all blockchains were somehow deleted and mine was the only one left)?

would really appreciate your help!!